Google: sys-kernel/cchost-kernel-6_18, sys-kernel/csql-kernel-6_18, sys-kernel/lakitu-kernel-6_18, sys-kernel/lakitu-nc-kernel-6_18: security update to 20162.0.0

high Tenable Self-Hosted Container Security Plugin ID 475797

Description

There are packages installed that are affected by a vulnerability referenced in the following CVE:

- In the Linux kernel, the following vulnerability has been resolved: smb: client: clear setuid/setgid bit
on write with cifsacl/modefromsid/posix extensions When a file has the setuid or setgid bit set and is
written to, the VFS strips those bits and issues a setattr with ATTR_KILL_SUID/ATTR_KILL_SGID together
with an ATTR_MODE carrying the already-cleared mode. Both cifs_setattr_unix() and cifs_setattr_nounix()
unconditionally dropped ATTR_MODE in that case: /* skip mode change if it's just for clearing
setuid/setgid */ if (attrs->ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID)) attrs->ia_valid &= ~ATTR_MODE;
This is fine for the default mount, where the mode is only emulated via the DOS read-only attribute and
cannot represent the setuid/setgid bits anyway. However, with the "cifsacl" or "modefromsid" mount options
the mode is stored on the server through an ACL (id_mode_to_cifs_acl()), with the SMB3.1.1 POSIX
extensions the mode is sent to the server directly, and with the SMB1 Unix extensions (cifs_setattr_unix)
the mode is sent via CIFSSMBUnixSetPathInfo(). In all those cases dropping ATTR_MODE means the cleared
mode is never pushed to the server, so the setuid/setgid bit survives the write. This is a security issue:
on local filesystems the setuid bit is stripped when a file is written, but over these cifs.ko mounts the
bit persists on the server, potentially allowing an unexpected privilege escalation on subsequent
execution. Fix this in two places: 1. cifs_setattr_nounix(): only take the "skip mode change" shortcut
when the mode is emulated via the DOS read-only attribute (i.e. neither cifsacl/modefromsid nor the
SMB3.1.1 POSIX extensions are in effect), so that the cleared mode is propagated to the server in the ACL
/ POSIX cases. 2. cifs_setattr_unix(): this function is only called when Unix extensions are in effect, so
the mode is always stored on the server. Remove the shortcut entirely so that the cleared mode is always
pushed. (CVE-2026-89638)

Solution

Update the sys-kernel/cchost-kernel-6_18 library and its related packages to version 20162.0.0 or later.

Plugin Details

Severity: High

ID: 475797

Version: Revision 1.1

Type: Local

Family: Google COS Security Checks

Published: 10/16/2026

Updated: 10/16/2026

Risk Information

VPR

Risk Factor: Medium

Score: 4.9

Percentile: 58.39

Vendor

Vendor Severity: LOW

CVSS v2

Risk Factor: Medium

Base Score: 6.8

Temporal Score: 5

Vector: CVSS2#AV:L/AC:L/Au:S/C:C/I:C/A:C

CVSS Score Source: CVE-2026-89638

CVSS v3

Risk Factor: High

Base Score: 7.8

Temporal Score: 6.8

Vector: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Temporal Vector: CVSS:3.0/E:U/RL:O/RC:C

Vulnerability Information

Exploit Ease: No known exploits are available

Vulnerability Publication Date: 9/11/2026

Reference Information

CVE: CVE-2026-89638

Detections

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